File recovery utility for CBM disks?

Hi, All,

I've looked around and can't find a tool for this, but there must be
one.  I have a .d64 disk image where I think the original disk had
media failure on track 18.  I can see a large number of meaningful
strings if I hexdump the file, so there are (or were) real contents.
I'm looking for a tool that will look at the first two bytes of every
sector, and if not 00 00, chase the pointers to figure out the forward
chain and note which track/sector is the start of the chain.

I could write such a utility in any number of  languages, but of
course, I'd rather just use an existing tool.  It doesn't matter to me
if said tool runs "native" on some CBM platform, or if it's a tool for
UNIX, etc, that operates on disk images, the result is the same -
either a list of file "heads" or, even better, a reconstructed
directory track with dummy file names.

I don't mind inventing the wheel, but prefer not to re-invent it. Can
anyone point me to some kind of diskette/image file recovery tool?

-ethan